Stem cells by themselves aren't going some of the big problems with aging and damaged tissue. Tissue engineering is needed to create 3-D environments that guide creation of replacement organs and other body parts. Some Johns Hopkins researchers have developed 3-D nanofiber scaffolds
In the laboratory, the researchers created a nanofiber-based network using a process called electrospinning, which entails shooting a polymer stream onto a charged platform, and added chondroitin sulfate—a compound commonly found in many joint supplements—to serve as a growth trigger. After characterizing the fibers, they made a number of different scaffolds from either spun polymer or spun polymer plus chondroitin. They then used goat bone marrow-derived stem cells (a widely used model) and seeded them in various scaffolds to see how stem cells responded to the material.
Elisseeff and her team watched the cells grow and found that compared to cells growing without scaffold, these cells developed into more voluminous, cartilage-like tissue. "The nanofibers provided a platform where a larger volume of tissue could be produced," says Elisseeff, adding that 3-dimensional nanofiber scaffolds were more useful than the more common nanofiber sheets for studying cartilage defects in humans.
The many people who live in pain due to damaged cartilage would benefit from the ability to grow more cartilage.
Nanofiber scaffolds improved higher quality cartilage production in rats.
The investigators then tested their system in an animal model. They implanted the nanofiber scaffolds into damaged cartilage in the knees of rats, and compared the results to damaged cartilage in knees left alone.
They found that the use of the nanofiber scaffolds improved tissue development and repair as measured by the production of collagen, a component of cartilage. The nanofiber scaffolds resulted in greater production of a more durable type of collagen, which is usually lacking in surgically repaired cartilage tissue. In rats, for example, they found that the limbs with damaged cartilage treated with nanofiber scaffolds generated a higher percentage of the more durable collagen (type 2) than those damaged areas that were left untreated.
Since we have cartilage in so many joints we really need a way to cause cartilage repair without the need for surgery to deliver a scaffolding or new cartilage into each aged and worn joint.
Orthopedic implants dipped in growth factors stimulate bone, blood vessel, or cartilage growth.
MADISON – When William Murphy works with some of the most powerful tools in biology, he thinks about making tools that can fit together. These constructions sound a bit like socket wrenches, which can be assembled to turn a half-inch nut in tight quarters, or to loosen a rusted-tight one-inch bolt using a very persuasive lever.
The tools used by Murphy, an associate professor of biomedical engineering and orthopedics and rehabilitation at University of Wisconsin-Madison, however, are proteins, which are vastly more flexible than socket wrenches -- and roughly 100 million times smaller. One end of his modular tool may connect to bone, while the other end may stimulate the growth of bone, blood vessels or cartilage.
To grow replacement tissue in situ (in place in our bodies) we need the ability to create 3-dimensional biochemical environments that orchestrate the right sequence of signals to guide tissue growth to repair damaged areas. While stem cells get a great deal of attention for many types of damage the problem isn't the lack of cells to do the repair. Rather, the challenge is to guide cells so they go to the right places and create the right 3-dimensional structures.
On February 4th and 6th, at the Orthopedic Research Society meeting in San Francisco, Darilis Suarez-Gonzalez and Jae Sung Lee of the Murphy lab are reporting that orthopedic implants "dip-coated" with modular growth factors can stimulate bone and blood vessel growth in sheep.
For many years, medical scientists have been fascinated by growth factors -- proteins that can stimulate tissues to grow. But these factors can be too effective or not specific enough, leading to cancer rather than the controlled growth needed for healing.
What's still needed: variable control of which signals get sent thru time. What happens naturally during development where limbs and organs grow is much harder to bring about for one area in an already adult body. All the cells in developing tissue send signals that coordinate their changes in a very complex sequence. Replicating that is not easy. Also, the adult tissue contains plenty of aged cells that are not functioning optimally. More youthful replacement cells would do a better job of repair.